1. Field of the Invention
The present invention relates to a pulp molding and, more particularly, to a pulp molding alternative to foam styrene resin materials.
2. Description of the Related Art
Packings of foam styrene resin having excellent cushioning characteristics have been used in packing electric apparatus including television sets and video tape recorders. However, environmental pollution attributable to waste packings of foam styrene resin have become a serious problem because foam styrene resin is unperishable and undecomposable in soil and produces noxious gases when incinerated. Accordingly, the development of pollution-free packing materials alternative to foam styrene resin packing materials has been desired. One of the remarkable alternative packing materials is a pulp molding formed by molding a feedstock produced by processing waste paper, such as newspaper, as a principal raw material, and pulp packings formed by molding pulp materials have been used for packing small electric apparatus including cassette tape recorders.
A pulp molding currently used as a pulp packing contains, as principal components, pulp and a vinyl acetate copolymer containing ethylene serving as a synthetic binder. This vinyl acetate copolymer is used widely for paint and adhesives. The material of the pulp molding contains the synthetic binder to enhance the water resistance of the pulp molding. Generally, the pulp molding contains 8% by weight synthetic binder. However, the cushioning property of the pulp molding formed of the conventional material is not sufficiently high and such a pulp molding is not suitable for packing large electric apparatus including television sets and video tape recorders.
If the vinyl acetate resin content of the pulp molding is 8% by weight to reduce the hygroscopicity of the pulp molding, it is difficult to deflocculate the pulp molding for reclamation because the binder is difficult to resolve in water. Furthermore, the effect of the binder on the reduction of the hygroscopicity of the pulp molding is insignificant; for example, while the moisture percentage of a pulp molding not containing any binder is 10.8% when the same is kept for a predetermined time in an environment of a temperature of 60.degree. C. and a relative humidity of 80%, the moisture percentage of the pulp molding containing 8% by weight binder kept in the same environment is 9%. Thus, the physical properties of the pulp molding are liable to deteriorate in a high-temperature high-humidity environment.